14 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



1959 PRODUCTION 



By the end of December 1959, an estimated 767,- 

 071 bait-size (1.5 to 2.1 in.) tilapia weighing 2,489 

 pounds (356 buckets) had been removed from the 

 hatchery. Of this amount 508,364 fish weighing 

 1,-415 pounds (202 bucitets) were delivered to Maui 

 Fisheries and Marine Products, Ltd. A few buck- 

 ets of fish were supplied to the Hawaii Division 

 of Fish and Game for experimental purposes. The 

 rest were used from the )Stnifh and GUhert. The 

 average individual weight of fish in each of the 

 delivered lots, estimated by subsampling, ranged 

 from 0.92 g. (37 mm. or 1.5 in. length) to 2.67 

 g. (52 mm. or 2.1 in. length). The average of 

 all lots was 1.49 g. (43 mm. or 1.7 in. length). 

 Of the total bait delivered, 159,504 fish or 971 

 pounds were carried over from the 1958 produc- 

 tion. 



The total production for 1959 was 1,293,734 frj'. 

 If we subtract the observed mortalities (99,209) 

 and fish delivered (607,567) from the total pro- 

 duction, we have a remainder of 586,958 fish. An 

 estimated 514,900 fry remained in the hatchery as 

 of December 8, 1959. The diflference tetween 

 586,958 and 514,900 is 72,058 fish, representing the 

 unobserved losses from cannibalism, predation by 

 night herons and dragonfly nymphs, and other 

 causes. In February 1960, 257 buckets of bait 

 should have been available at the hatcheiy. The 

 total bait delivered dunng 1959 was 1,517.9 pounds 

 (216.8 buckets), and the production was equal to 

 7,110 pounds (3.6 tons) per acre per year on an 

 area basis, or 15,600 pounds (7.8 tons) per acre 

 per year based on the total estimated production. 

 Production in numbers of young was higher in 

 1959 than in 1958, but production in buckets of 

 bait was about the same in the two years, since the 

 average size of the fish was smaller in 1959. The 

 smaller average size in 1959 may have resulted 

 from the less-frequent feeding and greater stock- 

 ing densities. 



There are numerous reports dealing with the 

 pond culture of tilapia. Chen (1953) reported an 

 annual production of 270 pounds per acre in the 

 rice paddies of Taiwan, and Pongsuwana (1956) 

 reported annual productions in excess of 5 tons 

 per acre in Thailand. Swingle (1960) reported 

 annual productions of 2,291 and 9,685 pounds per 

 acre in Alabama from stocking rates of 4,000 and 

 20,000 fingerlings i>er acre, respectively, basing the 

 production on 365 growing days a year. 



ACCLIMATIZATION TO SEA WATER 



The bait-size tilapia were hauled by truck from 

 the Paia hatchery to a docksite area, either to 

 Maalaea Harbor or to Kahului Harbor. Two 

 means were used to transport the fish: (1) 50- 

 gallon drums, each with a carrying capacity of 1 

 to 1.5 buckets of fish, and (2) a special truck bear- 

 ing a 500-gallon steel tank having a cari7ing 

 capacity of about 10 buckets of bait. 



The acclinuitization to sea water was carried out 

 either in large wooden tanks equipped with run- 

 ning fresh and salt water, located at Maalaea 

 Harbor ( fig. 9 ) , or in the bait wells of the sampans 

 and the Bureau of Commercial Fisheries vessels. 

 In each instance, the acclimatization was accom- 

 plished in 8 to 12 hours and with little loss of fish, 

 except for one unfortunate experience when an 

 entire lot of 129 pounds (27,000 fish) died. Mor- 

 tality in this case was probably the result of a 

 combination of factors : the rate of change from 

 fresh water to sea water was too rapid; there was 

 insufficient fresh water available to permit proper 

 acclimatization and the maintenance of suitable 

 oxygen concentrations; the vessel, lying at the 

 dock in Maalaea Harbor and, being held against 

 the dock by the wind, was generally motionless, so 

 there was "little circulation of water through holes 

 in tlie bottom of the bait wells. The loss was re- 

 grettable biit taught us several things about the 

 requirements and limitations of the fish that must 

 be considered during the acclimatization process. 



*^:~ 



Figure 9. — Tilapia acclimatization tanks at Maalaea 

 Harbor, Maui. 



